Toán Lớp 8: Bài 1: Thực hiện phép tính:
a) 2x(3×2 – 5x + 3) b) -2×2(x2 + 5x – 3) c) x2(2×3 – 4x + 3)
d) (2x – 1)(x2 + 5 – 4) e) 7x(x – 4) – (7x + 3)(2×2 – x + 4).
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Toán Lớp 8: Bài 1: Thực hiện phép tính:
a) 2x(3×2 – 5x + 3) b) -2×2(x2 + 5x – 3) c) x2(2×3 – 4x + 3)
d) (2x – 1)(x2 + 5 – 4) e) 7x(x – 4) – (7x + 3)(2×2 – x + 4).
Comments ( 1 )
a)2x\left( {3{x^2} – 5x + 3} \right)\\
= 2x.3{x^2} – 2x.5x + 2x.3\\
= 6{x^3} – 10{x^2} + 6x\\
b) – 2{x^2}\left( {{x^2} + 5x – 3} \right)\\
= – 2{x^2}.{x^2} – 2{x^2}.5x + 2{x^2}.3\\
= – 2{x^4} – 10{x^3} + 6{x^2}\\
c){x^2}\left( {2{x^3} – 4x + 3} \right)\\
= {x^2}.2{x^3} – {x^2}.4x + {x^2}.3\\
= 2{x^5} – 4{x^3} + 3{x^2}\\
d)\left( {2x – 1} \right)\left( {{x^2} + 5x – 4} \right)\\
= 2{x^3} + 10{x^2} – 8x – {x^2} – 5x + 4\\
= 2{x^3} + 9{x^2} – 13x + 4\\
e)7x\left( {x – 4} \right) – \left( {7x + 3} \right)\left( {2{x^2} – x + 4} \right)\\
= 7{x^2} – 28x – 14{x^3} + 7{x^2} – 28x – 6{x^2} + 3x – 12\\
= – 14{x^3} + 8{x^2} – 53x – 12
\end{array}$